Methods of fabricating polycrystalline diamond, and cutting elements and earth-boring tools comprising polycrystalline diamond

ABSTRACT

Methods of fabricating polycrystalline diamond include subjecting a particle mixture to high pressure and high temperature (HPHT) conditions to form inter-granular diamond-to-diamond bonds. Before being subjected to HPHT conditions, the particle mixture includes a plurality of non-diamond nanoparticles, diamond nanoparticles, and diamond grit. The non-diamond nanoparticles includes carbon-free cores and at least one functional group attached to the cores. Cutting elements for use in an earth-boring tool include a polycrystalline diamond material formed by such processes. Earth-boring tools include such cutting elements.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.14/885,161, filed Oct. 16, 2015, now U.S. Pat. No. 9,499,883, issuedNov. 22, 2016, which is a continuation of U.S. patent application Ser.No. 13/619,561, filed Sep. 14, 2012, now U.S. Pat. No. 9,309,582, issuedApr. 12, 2016, which application claims the benefit of U.S. ProvisionalPatent Application Serial No. 61/535,475, filed Sep. 16, 2011, in thename of DiGiovanni and Chakraborty, the disclosure of each of which ishereby incorporated herein in its entirety by this reference. U.S.patent application Ser. No. 14/885,161 is also a continuation-in-part ofU.S. patent application Ser. No. 14/607,227, filed Jan. 28, 2015, nowU.S. Pat. No. 9,283,657, issued Mar. 15, 2016, which is a divisional ofU.S. patent application Ser. No. 13/084,003, filed Apr. 11, 2011, nowU.S. Pat. No. 8,974,562, issued Mar. 10, 2015, which is acontinuation-in-part of U.S. patent application Ser. No. 13/077,426,filed Mar. 31, 2011, now U.S. Pat. No. 9,776,151, issued Oct. 3, 2017,which claims priority to U.S. Provisional Patent Application Ser. No.61/324,142, filed Apr. 14, 2010, the disclosure of each of which ishereby incorporated herein in its entirety by this reference.

The subject matter of this application is also related to the subjectmatter of U.S. patent application Ser. No. 13/619,210, filed Sep. 14,2012, now U.S. Pat. No. 9,205,531, issued Dec. 8, 2015, the disclosureof which is hereby incorporated herein in its entirety by thisreference. The subject matter of this application is also related to thesubject matter of U.S. patent application Ser. No. 13/316,094, filedDec. 9, 2011, now U.S. Pat. No. 10,005,672, issued Jun. 26, 2018, thedisclosure of which is hereby incorporated herein in its entirety bythis reference.

TECHNICAL FIELD

Embodiments of the present invention relate generally to methods offorming polycrystalline diamond material, cutting elements includingpolycrystalline diamond material, and earth-boring tools for drillingsubterranean formations including such cutting elements.

BACKGROUND

Earth-boring tools for forming wellbores in subterranean earthformations may include a plurality of cutting elements secured to abody. For example, fixed-cutter earth-boring rotary drill bits (alsoreferred to as “drag bits”) include a plurality of cutting elements thatare fixedly attached to a bit body of the drill bit. Similarly, rollercone earth-boring rotary drill bits include cones that are mounted onbearing pins extending from legs of a bit body such that each cone iscapable of rotating about the bearing pin on which the cone is mounted.A plurality of cutting elements may be mounted to each cone of the drillbit.

The cutting elements used in such earth-boring tools often includepolycrystalline diamond cutters (often referred to as “PDCs”), which arecutting elements that include a polycrystalline diamond (PCD) material.Such polycrystalline diamond cutting elements are formed by sinteringand bonding together relatively small diamond grains or crystals underconditions of high temperature and high pressure in the presence of acatalyst (such as cobalt, iron, nickel, or alloys and mixtures thereof)to form a layer of polycrystalline diamond material on a cutting elementsubstrate. These processes are often referred to as high pressure hightemperature (or “HPHT”) processes. The cutting element substrate maycomprise a cermet material (i.e., a ceramic-metal composite material)such as cobalt-cemented tungsten carbide. In such instances, the cobalt(or other catalyst material) in the cutting element substrate may bedrawn into the diamond grains or crystals during sintering and serve asa catalyst material for forming a diamond table from the diamond grainsor crystals. In other methods, powdered catalyst material may be mixedwith the diamond grains or crystals prior to sintering the grains orcrystals together in an HPHT process.

Upon formation of a diamond table using an HPHT process, catalystmaterial may remain in interstitial spaces between the grains orcrystals of diamond in the resulting polycrystalline diamond table. Thepresence of the catalyst material in the diamond table may contribute tothermal damage in the diamond table when the cutting element is heatedduring use, due to friction at the contact point between the cuttingelement and the formation. Polycrystalline diamond cutting elements inwhich the catalyst material remains in the diamond table are generallythermally stable up to a temperature of about 750° C., although internalstress within the polycrystalline diamond table may begin to develop attemperatures exceeding about 350° C. This internal stress is at leastpartially due to differences in the rates of thermal expansion betweenthe diamond table and the cutting element substrate to which it isbonded. This differential in thermal expansion rates may result inrelatively large compressive and tensile stresses at the interfacebetween the diamond table and the substrate, and may cause the diamondtable to delaminate from the substrate. At temperatures of about 750° C.and above, stresses within the diamond table may increase significantlydue to differences in the coefficients of thermal expansion of thediamond material and the catalyst material within the diamond tableitself. For example, cobalt thermally expands significantly faster thandiamond, which may cause cracks to form and propagate within a diamondtable including cobalt, eventually leading to deterioration of thediamond table and ineffectiveness of the cutting element.

To reduce the problems associated with different rates of thermalexpansion in polycrystalline diamond cutting elements, so-called“thermally stable” polycrystalline diamond (TSD) cutting elements havebeen developed. Such a thermally stable polycrystalline diamond cuttingelement may be formed by leaching the catalyst material (e.g., cobalt)out from interstitial spaces between the diamond grains in the diamondtable using, for example, an acid. All of the catalyst material may beremoved from the diamond table, or only a portion may be removed.Thermally stable polycrystalline diamond cutting elements in whichsubstantially all catalyst material has been leached from the diamondtable have been reported to be thermally stable up to temperatures ofabout 1200° C. It has also been reported, however, that such fullyleached diamond tables are relatively more brittle and vulnerable toshear, compressive, and tensile stresses than are non-leached diamondtables. In an effort to provide cutting elements having diamond tablesthat are more thermally stable relative to non-leached diamond tables,but that are also relatively less brittle and vulnerable to shear,compressive, and tensile stresses relative to fully leached diamondtables, cutting elements have been provided that include a diamond tablein which only a portion of the catalyst material has been leached fromthe diamond table.

BRIEF SUMMARY

In some embodiments of the disclosure, a method of fabricatingpolycrystalline diamond includes functionalizing surfaces of carbon-freenanoparticles with one or more functional groups, combining thefunctionalized nanoparticles with diamond nanoparticles and diamond gritto form a particle mixture, and subjecting the particle mixture to highpressure and high temperature (HPHT) conditions to form inter-granularbonds between the diamond nanoparticles and the diamond grit.

In some embodiments, a cutting element for use in an earth-boring toolincludes polycrystalline diamond material formed by a method comprisingfunctionalizing surfaces of carbon-free nanoparticles with one or morefunctional groups, combining the functionalized nanoparticles withdiamond nanoparticles and diamond grit to form a particle mixture, andsubjecting the particle mixture to HPHT conditions to forminter-granular bonds between the diamond nanoparticles and the diamondgrit.

In some embodiments, an earth-boring tool includes a cutting element.The cutting element includes a polycrystalline diamond material formedby a method comprising functionalizing surfaces of carbon-freenanoparticles with one or more functional groups, combining thefunctionalized nanoparticles with diamond nanoparticles and diamond gritto form a particle mixture, and subjecting the particle mixture to HPHTconditions to form inter-granular bonds between the diamondnanoparticles and the diamond grit.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a partially cut-away perspective view of an embodiment of acutting element including a volume of polycrystalline diamond on asubstrate;

FIG. 2 is a simplified view illustrating how a microstructure of thepolycrystalline diamond of the cutting element of FIG. 1 may appearunder magnification;

FIGS. 3A through 3D illustrate the formation of a particle mixture bycombining functionalized nanoparticles with diamond nanoparticles anddiamond grit for use in forming polycrystalline diamond of the cuttingelement of FIG. 1;

FIG. 4 is a simplified cross-sectional view illustrating materials usedto form the cutting element of FIG. 1, including the particle mixtureformed as described with reference to FIGS. 3A through 3D, in acontainer in preparation for subjecting the container to an HPHTsintering process;

FIGS. 5A and 5B illustrate the materials of FIGS. 3A through 3D beingencapsulated in the container of FIG. 4 in a gaseous environmentcomprising a hydrocarbon substance (e.g., methane) within an enclosedchamber; and

FIG. 6 illustrates an earth-boring rotary drill bit comprisingpolycrystalline diamond cutting elements as described herein.

DETAILED DESCRIPTION

The illustrations presented herein are not meant to be actual views ofany particular material, apparatus, system, or method, but are merelyidealized representations which are employed to describe certainembodiments of the present invention. For clarity in description,various features and elements common among the embodiments of theinvention may be referenced with the same or similar reference numerals.

FIG. 1 illustrates a cutting element 100, which may be formed inaccordance with embodiments of methods as disclosed herein. The cuttingelement 100 includes polycrystalline diamond 102. Optionally, thecutting element 100 also may include a substrate 104, to which thepolycrystalline diamond 102 may be bonded. For example, the substrate104 may include a generally cylindrical body of cobalt-cemented tungstencarbide material, although substrates of different geometries andcompositions also may be employed. The polycrystalline diamond 102 maybe in the form of a table (i.e., a layer) of polycrystalline diamond 102on the substrate 104, as shown in FIG. 1. The polycrystalline diamond102 may be provided on (e.g., formed on or secured to) a surface of thesubstrate 104. In additional embodiments, the cutting element 100 maysimply comprise a volume of the polycrystalline diamond 102 having anydesirable shape, and may not include any substrate 104.

As shown in FIG. 2, the polycrystalline diamond 102 may includeinterspersed and interbonded diamond grains that form athree-dimensional network of diamond material. Optionally, in someembodiments, the diamond grains of the polycrystalline diamond 102 mayhave a multimodal grain size distribution. For example, thepolycrystalline diamond 102 may include larger diamond grains 106 andsmaller diamond grains 108. The larger diamond grains 106 and/or thesmaller diamond grains 108 may have average particle dimensions (e.g.,mean diameters) of less than 1 mm, less than 0.1 mm, less than 0.01 mm,less than 1 μm, less than 0.1 μm, or even less than 0.01 μm. That is,the larger diamond grains 106 and smaller diamond grains 108 may eachinclude micron diamond particles (diamond grains in a range from about 1μm to about 500 μm (0.5 mm)), submicron diamond particles (diamondgrains in a range from about 500 nm (0.5 μm) to about 1 μm), and/ordiamond nanoparticles (particles having an average particle diameter ofabout 500 nm or less). In some embodiments, the larger diamond grains106 may be micron diamond particles, and the smaller diamond grains 108may be submicron diamond particles or diamond nanoparticles. In someembodiments, the larger diamond grains 106 may be submicron diamondparticles, and the smaller diamond grains 108 may be diamondnanoparticles. In other embodiments, the diamond grains of thepolycrystalline diamond 102 may have a monomodal grain sizedistribution. The direct diamond-to-diamond inter-granular bonds betweenthe diamond grains 106, 108 are represented in FIG. 2 by dashed lines110. Interstitial spaces 112 (shaded black in FIG. 2) are presentbetween the interbonded diamond grains 106, 108 of the polycrystallinediamond 102. These interstitial spaces 112 may be at least partiallyfilled with a solid substance, such as a metal solvent catalyst (e.g.,iron, cobalt, nickel, or an alloy or mixture thereof) and/or acarbon-free material. In other embodiments, the interstitial spaces 112may include empty voids within the polycrystalline diamond 102 in whichthere is no solid or liquid substance (although a gas, such as air, maybe present in the voids). Such empty voids may be formed by removing(e.g., leaching) solid material out from the interstitial spaces 112after forming the polycrystalline diamond 102. In yet furtherembodiments, the interstitial spaces 112 may be at least partiallyfilled with a solid substance in one or more regions of thepolycrystalline diamond 102, while the interstitial spaces 112 in one ormore other regions of the polycrystalline diamond 102 include emptyvoids.

Embodiments of methods disclosed herein may be used to form thepolycrystalline diamond 102, and may result in improved inter-granulardiamond-to-diamond bonding between the diamond grains 106, 108 in thepolycrystalline diamond 102.

Carbon-free particles (e.g., nanoparticles, submicron particles, and/ormicron-sized particles) may be functionalized with diamond precursorfunctional groups and mixed with diamond particles (e.g., nanoparticles,submicron particles, and/or micron-sized particles) before the diamondparticles are subjected to HPHT processing to form the polycrystallinediamond 102. FIGS. 3A-3D illustrate example embodiments of methods thatmay be used to form a particle mixture to be subjected to HPHTconditions to form polycrystalline diamond 102.

FIG. 3A shows a simplified view of diamond nanoparticles 130. Thediamond nanoparticles 130 may be mono-modal or multi-modal (includingbimodal). In some embodiments, the diamond nanoparticles 130 may includean outer carbon shell, which may be referred to in the art as a carbon“onion.” In other embodiments, the diamond nanoparticles 130 may notinclude any such outer carbon shell.

As shown in FIG. 3B, the diamond nanoparticles 130 may be combined andmixed with functionalized nanoparticles 131 having a carbon-free core toform a first particle mixture 132. The functionalized nanoparticles 131may have a core including, for example, metal or a metal alloy. Themetal or metal alloy may be, for example, iron, cobalt, nickel, or analloy or mixture of such metals. Such metals may serve as a solventmetal catalyst for the formation of the direct diamond-to-diamondinter-granular bonds, as known in the art. In additional embodiments,the functionalized nanoparticles 131 may have a core including a ceramicmaterial such as an oxide (e.g., alumina, (Al₂O₃) magnesia (MgO), etc.)or a nitride.

As non-limiting examples, the core may be functionalized with afunctional group, such as a methyl functional group or an acetylenefunctional group. Functional groups that include carbon and hydrogen mayenhance the formation of inter-granular diamond-to-diamond bonds betweenthe diamond grains 106, 108 in the polycrystalline diamond 102 (FIG. 2).Without being bound to a particular theory, the hydrogen in the chemicalfunctional group may provide a reducing atmosphere in the vicinity ofthe diamond particles at HPHT conditions. For example, at HPHTconditions, the functional groups may at least partially dissociate ordecompose. Products of such decomposition may include elemental carbonand hydrogen.

In some embodiments, carbon-free cores (e.g., carbon-free nanoparticles,such as ceramic nanoparticles) may be functionalized by exposing thecarbon-free cores to functional groups including carbon and hydrogen.For example, the functional group may be a methyl group, provided byexposing the carbon-free cores to a methane gas environment. The methanegas may form carbon-based functional groups on the carbon-free cores bychemical vapor deposition (CVD). In certain embodiments, nanoparticlesmay be treated with acid, then encapsulated with a polymer. Such aprocess is described in A. R. Mandavian et al., “Nanocomposite particleswith core-shell morphology III: preparation and characterization of nanoAl₂O₃—poly(styrene-methyl methacrylate) particles via miniemulsionpolymerization,” 63 POLYMER BULLETIN 329-340 (2009), which isincorporated herein in its entirety by this reference. In otherembodiments, the carbon-free cores may be functionalized usingtechniques such as those disclosed in, for example, U.S. PatentApplication Publication No. 2011/0252711, published Oct. 20, 2011, andentitled “Method of Preparing Polycrystalline Diamond from DerivatizedNanodiamond,” the disclosure of which is incorporated herein in itsentirety by this reference.

In some embodiments, functionalized nanoparticles 131 having differentfunctional groups may be admixed before mixing the functionalizednanoparticles 131 with the diamond nanoparticles 130. For example,functionalized nanoparticles 131 having a first functional group may beadmixed in any proportion with functionalized nanoparticles 131 having asecond functional group. Thus, the amount of each functional group inthe mixture of functionalized nanoparticles 131 and in the resultingfirst particle mixture 132 may be selected or tailored. The particularfunctional group or combination of functional groups may be selected tohave a selected ratio of carbon atoms to hydrogen atoms. For example,the functional group or combination of functional groups may have aratio of carbon atoms to hydrogen atoms from about 1:1 to about 1:3,such as from about 1:2 to about 1:3.

The first particle mixture 132, shown in FIG. 3B, may be formed, forexample, by suspending the functionalized nanoparticles 131 and thediamond nanoparticles 130 in a liquid to form a suspension. Thesuspension may be dried, leaving behind the first particle mixture 132,which may be in the form of a powder product (e.g., a powder cake). Thedrying process may include, for example, one or more of a spray-dryingprocess, a freeze-drying process, a flash-drying process, or any otherdrying process known in the art.

Optionally, the first particle mixture 132 may be crushed, milled, orotherwise agitated so as to form relatively small clusters oragglomerates 133 of the first particle mixture 132, as shown in FIG. 3C.The agglomerates 133 of the first particle mixture 132 may be combinedand mixed with relatively larger diamond particles 134 (i.e., diamond“grit”) to form a second particle mixture 135, as shown in FIG. 3D. As anon-limiting example, the relatively larger diamond particles 134 may bemicron diamond particles and/or submicron diamond particles, having anaverage particle size of between about five hundred nanometers (500 nm)and about ten microns (10 μm). The relatively larger diamond particles134, like the diamond nanoparticles 130, may or may not include an outercarbon shell.

In additional embodiments, the second particle mixture 135 may be formedby suspending the relatively larger diamond particles 134 in a liquidsuspension together with the diamond nanoparticles 130 and thefunctionalized nanoparticles 131, and subsequently drying the liquidsuspension using a technique such as those previously disclosed. In suchmethods, distinct first and second particle mixtures may not beproduced, as the diamond nanoparticles 130, the functionalizednanoparticles 131, and the relatively larger diamond particles 134 maybe combined together in a single liquid suspension, which may be driedto form the second particle mixture 135 directly.

The second particle mixture 135 thus includes the diamond nanoparticles130, the functionalized nanoparticles 131, and the larger diamondparticles 134. The second particle mixture 135 then may be subjected toHPHT processing to form polycrystalline diamond 102. Optionally, thesecond particle mixture 135 may be subjected to a milling process priorto subjecting the second particle mixture 135 to an HPHT process.

In some embodiments, the HPHT conditions may comprise a temperature ofat least about 1400° C. and a pressure of at least about 5.0 GPa.

Referring to FIG. 4, the particle mixture 135 may be positioned within acanister 118 (e.g., a metal canister). The particle mixture 135 includesthe diamond nanoparticles 130 and the relatively larger diamondparticles 134, which will ultimately form the diamond grains 108, 106,respectively, in the polycrystalline diamond 102 (FIG. 2) duringsintering. The particle mixture 135 also includes the functionalizednanoparticles 131.

As shown in FIG. 4, the canister 118 may include an inner cup 120 inwhich the particle mixture 135 may be disposed. If the cutting element100 is to include a substrate 104, the substrate 104 optionally may beprovided in the inner cup 120 over or under the particle mixture 135,and may ultimately be encapsulated in the canister 118. The canister 118may further include a top end piece 122 and a bottom end piece 124,which may be assembled and bonded together (e.g., swage bonded) aroundthe inner cup 120 with the particle mixture 135 and the optionalsubstrate 104 therein. The sealed canister 118 then may be subjected toan HPHT process to form the polycrystalline diamond 102.

In some embodiments, a hydrocarbon substance, such as methane gas,another hydrocarbon, or a mixture of hydrocarbons, also may beencapsulated in the canister 118 in the spaces between the variousparticles in the particle mixture 135. Methane is one of the primarycarbon sources used to form films of polycrystalline diamond in CVDprocesses. The hydrocarbon substance, if used, may be infiltrated intothe canister 118 (e.g., the inner cup 120 of the canister 118) in whichthe particle mixture 135 is present. The canister 118 may then be sealedwith the particle mixture 135 and the hydrocarbon substance therein. Thehydrocarbon substance may be introduced after performing a vacuumpurification process (e.g., after exposing the particle mixture 135and/or the canister 118 to a reduced-pressure (vacuum) environment at aselected temperature to evaporate volatile compounds) on the particlemixture 135 to reduce impurities within the canister 118. Thehydrocarbon substance may also be introduced into the canister 118 underpressure, such that the concentration of the hydrocarbon substance isselectively controlled prior to sealing the canister 118 and subjectingthe sealed canister 118 to HPHT conditions. In other words, byselectively controlling the pressure (e.g., partial pressure) of thehydrocarbon substance, the concentration of the hydrocarbon substance inthe sealed container 118 also may be selectively controlled. In someembodiments in which the hydrocarbon substance introduced into thecanister 118 under pressure, the partial pressure of the hydrocarbonsubstance may be at least about 10 kPa, at least about 100 kPa, at leastabout 1000 kPa (1.0 MPa), at least about 10 MPa, at least about 100 MPa,or even at least about 500 MPa.

The temperature of the particle mixture 135, the optional hydrocarbonsubstance, and the canister 118 may be selectively controlled prior tosealing the canister 118 and subjecting the sealed canister 118 to HPHTconditions. For example, a hydrocarbon substance may be introduced andthe canister 118 sealed at temperatures, for example, of less than −150°C., less than −161° C., or less than −182° C. In some embodiments, thehydrocarbon substance may be introduced at temperatures of about −196°C. (77 K) or even about −269° C. (4.2 K), temperatures of liquidnitrogen and liquid helium, respectively. At such temperatures, thehydrocarbon substance may be liquid or solid, and sealing the canister118 with the hydrocarbon substance may be relatively simpler thansealing a gaseous hydrocarbon substance in the canister 118. Inparticular, if the hydrocarbon substance is methane, the methane may bein liquid form at temperatures less than −161° C. and in solid form attemperatures less than −182° C., the boiling point and melting point,respectively, of methane. Appropriate temperatures at which otherhydrocarbon substances are in liquid or solid form may be selected by aperson having ordinary skill in the art, and are not tabulated herein.

FIG. 5A illustrates the particle mixture 135 disposed within an innercup 120 of the canister 118 (FIG. 4) in an enclosed chamber 128. Thehydrocarbon substance may be introduced into the enclosed chamber 128through an inlet 139, as illustrated by the directional arrow in FIG.5A. The pressure of the hydrocarbon substance within the enclosedchamber 128 may be selectively controlled (e.g., increased) toselectively control the amount of the hydrocarbon substance to beencapsulated within the canister 118 (FIG. 4). For example, the pressureof the hydrocarbon substance within the enclosed chamber 128 may be atleast about 10 kPa, at least about 100 kPa, at least about 1000 kPa (1.0MPa), at least about 10 MPa, at least about 100 MPa, or even at leastabout 500 MPa.

Referring to FIG. 5B, the canister 118 may be assembled within theenclosed chamber 128 to encapsulate the particle mixture 135 and thehydrocarbon substance present in the gaseous environment in the enclosedchamber 128 within the canister 118. The sealed canister 118 then may besubjected to HPHT processing.

In some embodiments, the hydrocarbon substance can be introduced intothe canister 118 to be subjected to the HPHT processing after placingthe particle mixture 135 in the canister 118. In other embodiments, thehydrocarbon substance may be introduced to the particle mixture 135 in aseparate container prior to inserting the particle mixture 135 into thecanister 118 to be subjected to HPHT processing. In such embodiments,the particle mixture 135 may remain in a hydrocarbon environment untilit is sealed in the canister 118 to be subjected to HPHT processing.

In additional embodiments of the disclosure, the hydrocarbon substancemay be mixed with the particle mixture 135 and sealed in the canister118 to be subjected to HPHT processing while the hydrocarbon substanceis in a solid or liquid state. For example, the hydrocarbon substancemay be a compressed liquid or solid or a complex of a hydrocarbon withanother material. In some embodiments, the hydrocarbon substance mayinclude a hydrated hydrocarbon, such as methane hydrate (i.e., methaneclathrate), ethane hydrate, etc. Methane hydrate, other hydrocarbonhydrates, or other forms of hydrocarbon mixtures that may be in a liquidor solid form may be introduced with the particle mixture 135.Introducing the hydrocarbon substance may optionally be performed attemperatures below room temperature (e.g., at cryogenic temperatures).For example, the hydrocarbon substance may be introduced with theparticle mixture 135 at temperatures at which the hydrocarbon substanceforms a liquid or solid, for example, temperatures of less than −150°C., less than −161° C., or less than −182° C.

Without being bound by any particular theory, it is believed that thefunctional groups on the functionalized nanoparticles 131 and theoptional hydrocarbon substance promote the formation ofdiamond-to-diamond inter-granular bonds 110 between the diamond grains106, 108, as shown in FIG. 2. For example, the functional groups and thehydrocarbon substance may dissociate in HPHT conditions. Each carbonatom, after dissociation, may bond with one or more of the diamondparticles (e.g., diamond nanoparticles 130 or relatively larger diamondparticles 134 (FIG. 3D)). The hydrogen atoms, after dissociation, mayform hydrogen gas (H₂), which may be a reducing agent. Some hydrogen gasmay react with impurities or catalyst material (if present) within thepolycrystalline diamond 102. Some hydrogen gas may diffuse out of thepolycrystalline diamond 102 and may react with material of the canister118. Some hydrogen gas may bond to exposed surfaces of thepolycrystalline diamond 102 to form hydrogen-terminated polycrystallinediamond.

Embodiments of cutting elements 100 (FIG. 1) that includepolycrystalline diamond 102 fabricated as described herein may bemounted to earth-boring tools and used to remove subterranean formationmaterial in accordance with additional embodiments of the presentdisclosure. FIG. 6 illustrates a fixed-cutter earth-boring rotary drillbit 160. The drill bit 160 includes a bit body 162. A plurality ofcutting elements 100 as described herein may be mounted on the bit body162 of the drill bit 160. The cutting elements 100 may be brazed orotherwise secured within pockets formed in the outer surface of the bitbody 162. Other types of earth-boring tools, such as roller cone bits,percussion bits, hybrid bits, reamers, etc., also may include cuttingelements 100 as described herein.

Polycrystalline diamond 102 (FIGS. 1 and 2) fabricated using methods asdescribed herein may exhibit improved abrasion resistance and thermalstability.

Additional non-limiting example embodiments of the disclosure aredescribed below.

Embodiment 1: A method of fabricating polycrystalline diamond,comprising functionalizing surfaces of carbon-free nanoparticles withone or more functional groups, combining the functionalizednanoparticles with diamond nanoparticles and diamond grit to form aparticle mixture, and subjecting the particle mixture to HPHT conditionsto form inter-granular bonds between the diamond nanoparticles and thediamond grit.

Embodiment 2: The method of Embodiment 1, wherein functionalizing thesurfaces of the carbon-free nanoparticles with one or more functionalgroups comprises functionalizing the surfaces of the carbon-freenanoparticles with methyl functional groups.

Embodiment 3: The method of Embodiment 1 or Embodiment 2, whereinfunctionalizing the surfaces of the carbon-free nanoparticles with oneor more functional groups comprises functionalizing the surfaces of thecarbon-free nanoparticles with acetylene functional groups.

Embodiment 4: The method of any of Embodiments 1 through 3, furthercomprising selecting the carbon-free nanoparticles to comprise a metalor a metal alloy.

Embodiment 5: The method of Embodiment 4, further comprising selectingthe carbon-free nanoparticles to comprise one or more of iron, cobalt,and nickel.

Embodiment 6: The method of any of Embodiments 1 through 3, furthercomprising selecting the carbon-free nanoparticles to comprise a ceramicmaterial.

Embodiment 7: The method of Embodiment 6, further comprising selectingthe carbon-free nanoparticles to comprise one or more of an oxide and anitride.

Embodiment 8: The method of Embodiment 6 or Embodiment 7, furthercomprising selecting the carbon-free nanoparticles to comprise aluminaor magnesia.

Embodiment 9: The method of any of Embodiments 1 through 8, whereincombining the functionalized nanoparticles with the diamondnanoparticles and the diamond grit to form the particle mixturecomprises suspending the functionalized nanoparticles and the diamondnanoparticles in a liquid to form a suspension and drying thesuspension.

Embodiment 10: The method of Embodiment 9, wherein drying the suspensioncomprises one or more of spray drying, freeze drying, and flash dryingthe suspension.

Embodiment 11: The method of Embodiment 9 or Embodiment 10, furthercomprising suspending the diamond grit in the liquid.

Embodiment 12: The method of any of Embodiments 9 through 11, whereindrying the suspension comprises drying the suspension to form a powderproduct.

Embodiment 13: The method of Embodiment 12, further comprising mixingthe powder product with the diamond grit to form the particle mixture.

Embodiment 14: The method of Embodiment 13, further comprising millingthe particle mixture prior to subjecting the particle mixture to theHPHT conditions.

Embodiment 15: The method of Embodiment 12, further comprising millingthe powder product.

Embodiment 16: The method of any of Embodiments 1 through 15, whereinsubjecting the particle mixture to the HPHT conditions comprisessubjecting the particle mixture to a temperature of at least about 1400°C. and a pressure of at least about 5.0 GPa.

Embodiment 17: A cutting element for use in an earth-boring tool, thecutting element comprising a polycrystalline diamond material formed bya method comprising functionalizing surfaces of carbon-freenanoparticles with one or more functional groups, combining thefunctionalized nanoparticles with diamond nanoparticles and diamond gritto form a particle mixture, and subjecting the particle mixture to HPHTconditions to form inter-granular bonds between the diamondnanoparticles and the diamond grit.

Embodiment 18: The cutting element of Embodiment 17, whereinfunctionalizing the surfaces of the carbon-free nanoparticles with oneor more functional groups comprises functionalizing the surfaces of thecarbon-free nanoparticles with methyl or acetylene functional groups.

Embodiment 19: An earth-boring tool comprising a cutting element, thecutting element comprising a polycrystalline diamond material formed bya method comprising functionalizing surfaces of carbon-freenanoparticles with one or more functional groups, combining thefunctionalized nanoparticles with diamond nanoparticles and diamond gritto form a particle mixture, and subjecting the particle mixture to HPHTconditions to form inter-granular bonds between the diamondnanoparticles and the diamond grit.

Embodiment 20: The earth-boring tool of Embodiment 19, furthercomprising selecting the carbon-free nanoparticles to comprise aceramic, a metal, or a metal alloy.

Embodiment 21: The earth-boring tool of Embodiment 19 or Embodiment 20,wherein the earth-boring tool comprises an earth-boring rotary drillbit.

While the present invention has been described herein with respect tocertain embodiments, those of ordinary skill in the art will recognizeand appreciate that it is not so limited. Rather, many additions,deletions, and modifications to the embodiments depicted and describedherein may be made without departing from the scope of the invention ashereinafter claimed, and legal equivalents. In addition, features fromone embodiment may be combined with features of another embodiment whilestill being encompassed within the scope of the invention ascontemplated by the inventor. Further, the invention has utility indrill bits having different bit profiles as well as different cuttertypes.

What is claimed is:
 1. A method of fabricating polycrystalline diamond,comprising: subjecting a particle mixture to high pressure and hightemperature (HPHT) conditions to form inter-granular diamond-to-diamondbonds, wherein the particle mixture comprises, before subjecting to theHPHT conditions: a plurality of non-diamond nanoparticles, eachcomprising a carbon-free core and at least one functional group attachedthereto; diamond nanoparticles; and diamond grit.
 2. The method of claim1, further comprising functionalizing at least some of the plurality ofnon-diamond nanoparticles with functional groups formulated to formdiamond.
 3. The method of claim 1, further comprising functionalizing atleast some of the plurality of non-diamond nanoparticles with functionalgroups comprising carbon and hydrogen.
 4. The method of claim 1, whereinsubjecting a particle mixture to HPHT conditions comprises at leastpartially decomposing the at least one functional group.
 5. The methodof claim 4, wherein at least partially decomposing the at least onefunctional group comprises forming elemental carbon and elementalhydrogen.
 6. The method of claim 1, further comprising exposing thecarbon-free cores to a methane gas environment before subjecting theparticle mixture to HPHT conditions.
 7. The method of claim 6, whereinexposing the carbon-free cores to a methane gas environment comprisesforming carbon-based functional groups on the carbon-free cores bychemical vapor deposition (CVD).
 8. The method of claim 1, furthercomprising encapsulating at least some of the carbon-free cores in apolymer before subjecting the particle mixture to HPHT conditions. 9.The method of claim 1, further comprising forming the plurality ofnon-diamond nanoparticles to have a combination of at least twodifferent functional groups.
 10. The method of claim 1, wherein the atleast one functional group comprises carbon atoms and hydrogen atoms,and wherein a ratio of the carbon atoms to the hydrogen atoms is withina range from about 1:1 to about 1:3.
 11. The method of claim 1, furthercomprising forming agglomerates comprising the plurality of non-diamondnanoparticles and the diamond nanoparticles.
 12. The method of claim 11,further comprising mixing the agglomerates with the diamond grit. 13.The method of claim 1, further comprising encapsulating the particlemixture and a hydrocarbon substance in a canister before subjecting theparticle mixture to HPHT conditions.
 14. A cutting element for use in anearth-boring tool, the cutting element comprising a polycrystallinediamond material formed by a method comprising: subjecting a particlemixture to high pressure and high temperature (HPHT) conditions to forminter-granular diamond-to-diamond bonds, wherein the particle mixturecomprises, before subjecting to the HPHT conditions: a plurality ofnon-diamond nanoparticles, each comprising a carbon-free core and atleast one functional group attached thereto; diamond nanoparticles; anddiamond grit.
 15. The cutting element of claim 14, further comprising asubstrate, wherein the polycrystalline diamond material is bonded to thesubstrate.
 16. The cutting element of claim 15, wherein the substratecomprises a generally cylindrical body of cobalt-cemented tungstencarbide.
 17. The cutting element of claim 14, wherein the cuttingelement comprises a network of diamond grains having a bimodal sizedistribution.
 18. The cutting element of claim 17, wherein the networkof diamond grains comprises a first plurality of grains and a secondplurality of grains, the first plurality of grains having an averageparticle dimension from about 1 μm to about 500 μm, and the secondplurality of grains having an average particle dimension of about 500 nmor less.
 19. An earth-boring tool comprising a cutting element, thecutting element comprising a polycrystalline diamond material formed bya method comprising: subjecting a particle mixture to high pressure andhigh temperature (HPHT) conditions to form inter-granulardiamond-to-diamond bonds, wherein the particle mixture comprises, beforesubjecting to the HPHT conditions: a plurality of non-diamondnanoparticles, each comprising a carbon-free core and at least onefunctional group attached thereto; diamond nanoparticles; and diamondgrit.
 20. The earth-boring tool of claim 19, wherein the polycrystallinediamond comprises a generally cylindrical body bonded to a substratecomprising cobalt-cemented tungsten carbide.